1. Field of the Invention
The present invention relates to a solid-state imaging device, and more particularly to a structure of a waveguide above a light receiving part.
2. Description of the Related Art
A solid-state imaging device is used as an imaging device such as a digital still camera or a video camera. For example, a CMOS (Complementary Metal Oxide Semiconductor) sensor to be a type of a solid-state imaging device has a pixel region and a peripheral circuit region formed on a periphery thereof by defining a semiconductor substrate as a base. A plurality of photodiodes is formed in the pixel region. The photodiodes are provided corresponding to respective pixel parts and are disposed in a matrix along a main surface in a surface layer of the semiconductor substrate, for example.
A structure of a pixel region in a solid-state imaging device according to the related art will be described with reference to FIG. 7 by taking the structure disclosed in Japanese Patent No. 4117672 as an example.
As shown in FIG. 7, in a pixel part of the solid-state imaging device according to the related art, photodiode 903 is formed on a surface layer portion of one of main surfaces (a main surface on an upper side in a Z-axis direction) of semiconductor substrate 901. Insulating film 907 is provided on semiconductor substrate 901, and insulating films 909 and 911 are further provided thereon in sequence. Diffusion preventing films 908, 910 and 912 are formed between insulating film 907 and insulating film 909, between insulating film 909 and insulating film 911, and on insulating film 911, respectively. Moreover, wirings 913, 914 and 915 are formed downward in the Z-axis direction from boundary surfaces between insulating films 907, 909 and 911 and diffusion preventing films 908, 910 and 912, respectively.
A wiring layer to be a laminated product formed by insulating films 907, 909 and 911 and wirings 913, 914 and 915, and furthermore, diffusion preventing films 908, 910 and 912 has a concave portion formed in a place corresponding to a portion provided above photodiode 901. Passivation film 917 formed to cover diffusion preventing film 912 is formed to fill in the concave portion provided on the wiring layer. Passivation film 917 has a higher refractive index than insulating films 909 and 911, and incident light L91 is reflected by interface 917sf between passivation film 917 and insulating films 909 and 911 so that a leakage of light to the wiring layer is prevented to some degree. In other words, passivation film 917 is set to have a higher refractive index than insulating films 909 and 911 to constitute an optical waveguide above photodiode 903. Consequently, a light collection is carried out at a high efficiency.